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Materials Required for Mineral Wool External Wall Insulation

1. Priming the Substrate:

If you’re installing your Mineral Wool insulation system onto a brickwork substrate it will need priming with the Water Based Primer. We recommend applying this to the substrate by roller or brush. However, if you are rendering onto a very smooth substrate then we recommend applying the EWI-310 Universal Primer, as this contains aggregates which will provide a rough surface for the basecoat to adhere to. Ensuring that your substrate is adequately prepared is essential to ensuring that your render system will last.

Coverage rates:

5 litres covers 15-30m2 depending on the substrate.

Drying times:

1 coat takes 4 hours to dry.

2. Installing the Starter Track

When it comes to starter track, you have two options. Opt for aluminium starter track with a clip-on stop bead if you are looking to cut down on costs. Alternatively, if you want to ensure that thermal bridging is kept to an absolute minimum, we recommend using uPVC starter track. Both are available in a range of widths to house different thicknesses of insulation and are drilled into the wall above the DPC.

Coverage rates: 

UPVC starter track is available in 2m lengths.

Aluminium starter track is available in 2.5m lengths.

3. Preparing the Adhesive

Mineral Wool insulation is much heavier than EPS and therefore requires the use of EWI Pro’s strongest adhesive, the EWI-225 Premium Basecoat. This is a very versatile, dual-purpose product that can also be used in the subsequent basecoat layer. The EWI-225 is also breathable and therefore will not interfere with the vapour permeability of the Mineral Wool.

The adhesive is applied to the back of the board using the dot and dab method. This will allow you to get a nice flat surface for the render topcoat. 


1 x 25kg bag covers 4/5m2

Drying times: 

24-48 hours

4. Applying the Mineral Wool Insulation Boards

Mineral Wool insulation boards are high-performance and very effective. We sell Mineral Wool by the pack in a range of thicknesses. For insulating a solid brick wall the general recommendation to reach building regulations is to opt for a 110mm thickness. Mineral Wool can be tricky to install as you can’t rasp away imperfections (unlike EPS). A really flat surface will need to be achieved while mounting the boards to ensure a smooth topcoat. We recommend using a spirit level to regularly check that everything is flat. 



5. Installing the fixings

EWI Pro recommends that you install one fixing per corner, with an additional two in the middle of the insulation board. Metal fixings should be used with the Mineral Wool insulation system as they will support the weight of the boards. The fixings are available in a wide range of lengths to accommodate different thicknesses of insulation.

Alternatively, for advanced fire-safety, we recommend the use of our metal lamella firebreak fixings. These are great for insulating high-rise structures.


Metal pin screw fixings are the recommended fixing for Mineral Wool insulation. These come in boxes of 200 or 100 depending on the length.

7 fixings are required per m2.

6. Applying the Beading:

Beading is essential for reinforcing external areas that are more prone to damage, for example, the corners and the areas around windows and doors. The required beads will depend on the property and which particular areas need reinforcing. We have a broad range of render beads that should be selected and applied as necessary, our beads are uPVC and are designed to be embedded within the basecoat layer.

7. Applying the Basecoat:

For Mineral Wool external wall insulation systems, we recommend using the EWI-225 Premium Basecoat again for the basecoat layer, as this saves on material waste. EWI-225 should be applied at a thickness of 6mm.

Coverage rates:

1 x 25kg bag covers 4/5m2

Drying times:

24-48 hours

8. Embedding the Mesh:

Fibreglass Mesh is embedded within the basecoat for extra reinforcement. This will ensure the system remains crack resistant.

Coverage rates:

1 x 50m2 roll covers 42.5m2 when overlapped

Our standard mesh is sold either by the m2 or in rolls of 50m2.

9. Priming the Basecoat:

A render primer should be used to increase the adhesion of the render to the basecoat and can be tinted to match the colour of your render for increased opacity. The type of primer will depend on the type of render you are using. For a Silicone Silicate system, we recommend using the SiSi Render Primer which comes in two different bucket sizes.  


1 x 7L bucket covers 20m2

1 x 21L bucket covers 60-70m2

Drying times:

12-24 hours

10. Applying the Render Topcoat:

Once the primer is dry, the render topcoat can be applied. We recommend using either the Premium Bio Silicone Render, Silicone Render, or Silicone Silicate Render. These are intended for creating a decorative finish; they are through-coloured with grains suspended within the mixture in a range of different sizes to achieve the desired texture.

Premium Bio Silicone is our highest performing render, offering advanced self-cleaning capabilities that tackle any signs of organic growth on the substrate, and extra UV resistance for a long-lasting finish. Silicone Render is the ideal choice for a quality long-lasting finish as it has nano-silicone particles which are great for maintaining a clean facade. Silicone Silicate is excellent value, also offering vapour permeability. All of these options are highly flexible, so are ideal for ensuring that there are no problems with cracks.


1.0mm grain size: 1x25kg bucket covers c. 10m2

1.5mm grain size: 1x25kg bucket covers c. 7-10m2

Drying times:

24 hours (+)

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